How to rig a rotary counter?
Drive rotation of Empty2 by the rotation of Empty1


In Properties panel (N to toggle):


Right click on Y-Rotation axis of Empty2 and select Add Single Driver.

In the Drivers section of the Graph Editor:


Add a variable yrot, set Object to Empty1 and type to "Y-Rotation".
Set driver scripted expression to: pi * ((180.0 * yrot / pi) // 40 * 10) / 180.0



This will give you an increase of 10° on Y-Axis of Empty2 for every 40° on Y-Axis of Empty1



Looking at your image you'd do this for the Y-Axis of your empties.

If you need increments of 10 on different rotation speeds, change the 40 in the above formula to i.e. 50

You can chain empties setup like this by making the next empty always driven by the previous. So the variable you add should be chosen from the correct object. The formula stays the same.

The main driving power behind this step-wise driving is the // floor division operator, which does integer division.